a. Field of the Invention
The present invention relates to the field of shelters. More particularly, the present invention relates to in-ground shelters which either can be installed in new construction or can be retrofit, for example, in a garage in an existing residence. The present invention includes an improved sliding access door which allows for easier entrance and exit from the shelter than the prior art because the present invention has a larger opening and is unobtrusive because of its profile, substantially flush with the surrounding ground/floor level.
b. Description of the Prior Art
The idea of a shelter from dangerous forces such as tornadoes, hurricanes or bombs has been around for decades. See, for example, Pierson, U.S. Pat. No. 3,114,153 for a Combination Shelter and Swimming Pool. While less than optimally functional (what, for example, does one do about the water in the pool if one needs to use the shelter?), Pierson illustrates that the idea of an in-ground shelter is not new. Presumably, Pierson was focusing his efforts as a shelter that might protect a user from the threat of Soviet nuclear attack. Before Pierson, many people installed simple cellars primarily for food storage, but also for protection from storms. Entrance to these early shelters was usually accomplished by a hinged door.
More relevant to the present invention are Hope et al., U.S. Pat. No. 6,161,345, and Poole, U.S. Pat. No. 5,953,866. Hope et al., claimed a “tornado shelter,” and Poole claimed a “storm shelter.” Both are for a shelter which is designed to be installed below ground, and which has a sliding substantially flat access door near ground level to allow ingress and egress. The door in Poole, which is the patent closest to the present invention, appears to covers approximately one-third of the top of the shelter. The door sits on rollers, and rolls downwardly and inwardly to open. That is, it rolls down underneath of the rest of the shelter's top. This method of operation means that by rolling downwardly, it takes room out of an already cramped shelter, and by rolling under the lid, the size of the access door is limited because it must be smaller than the remaining portion of the top of the shelter under which it rolls. The opening in Hope's shelter cannot be larger than approximately one-half of the surface area of the top of the shelter. While an opening of this size may be sufficient for some purposes, for the disabled or for very large persons, it may be difficult to enter a shelter with such a limited opening size. Further, those who are claustrophobic would find such a shelter even more constricting knowing that the opening through which they have to pass out of the shelter is so small. Also, to the extent objects are to be taken into or stored in the shelter, the smaller opening makes putting them in or taking them out more difficult.
Poole claims a similar device, but the description in Poole and the drawings are much more limited. The opening covers about half of the top of the shelter area or less. There is no description in Poole about how the lid, as shown open in FIG. 6, is prevented from tipping over as it is opened. The force of gravity would, as shown in FIGS. 5 and 6 of Poole, force the leading edge of the lid to tip under its own weight. There is no structure shown or described in Poole which would prevent this from happening. Further, the Poole lid is well above ground level, which may prevent a vehicle from parking above the shelter if installed in a garage and which would also present a tripping hazard.
Ueno et al., U.S. Pat. No. 5,732,512 shows a manhole opening structure. While it is not directly related to the present art, it does allow access to an under-ground cavity, and it does have a substantially flat lid which opens to allow access. The problem with Ueno is that the lid slides on the ground. As the lid slides, it may slide over an uneven ground surface surrounding it, and the sliding would be less than uniform, especially given the debris that might gather around the shelter as a result of the storm. It would be very difficult to open a device such as one described by Ueno in a storm shelter context. Therefore, while Ueno is instructive, it does not show or describe the features of the claimed invention.